Fluorogenic molecules facilitate advanced biochemical and biological experiments. In particular, the ability to modify dyes using chemistry allows the construction of numerous probes for specific applications. For example, changing the chemical structure of fluorophores can allow fine-tuning of spectral properties. These fluorophores form a class of synthetic ion indicators that respond to changes in ion concentration, also known as chemosensors (FIG. 1A). The design and synthesis of such “smart” probes involves incorporation of ion recognition motifs into fluorophores. After incorporation, reversible binding of these ion recognition motifs to a specific ion alters the fluorescence output of the molecule through transient changes in absorption or fluorescence quantum yield.
This strategy has produced probes for many biologically relevant ions, including Na+, K+, Mg2+, Ca2+, and Zn2+, allowing non-invasive monitoring of ion concentration inside living cells. By allowing passive measurement of environmental changes in disparate contexts, including inside living cells, such probes have revolutionized biological research, facilitating a variety of key technologies including functional imaging of cellular activity in culture and in vivo. While this mode of sensing yields temporal information, it requires constant monitoring and complex setups to read out changes in ion concentration.
Another class of indicators includes chemodosimeters (i.e., reaction-based probes; FIG. 1B). In contrast to the transient change in fluorescence provided by chemosensor, the binding of an analyte to a chemodosimeters elicits an irreversible chemical reaction that alters fluorescence. This mode of sensing allows a simple endpoint measurement of fluorescence change, however, it also lacks the temporal granularity of reversible chemosensors.
Accordingly, there remains a need for compounds that have the temporal specificity of reversible chemosensors as well as the endpoint measurement capabilities of chemodosimeter systems.